A vehicle air conditioner for minimizing the leakage of air through a dual blocking structure between upper and lower flow paths, and having a dual blocking structure. An air-conditioning case having an inner air flow path is divided into an upper flow path and a lower flow path. A heat exchanger for cooling and a heat exchanger for heating are provided in the air flow path of the air-conditioning case. A member having through-holes is disposed downstream of the heat exchanger for heating in the flow direction of air and allows the air that has passed through the heat exchanger for heating to pass therethrough. The member having through-holes has a horizontal member dividing the upper flow path from the lower flow path. A leakage-preventing means is overlapped with the horizontal member so as to prevent the air in the upper flow path and the lower flow path from mixing.